1. Field of the Invention
The present invention relates to a method and apparatus for upsetting end portions of pipe and particularly oilfield pipe to provide an increased wall thickness end portion for receiving tool joints or making threaded connectors on the pipe ends.
2. Description of the Prior Art
Oilfield tubulars which are typically connected together end to end by threaded couplings have, for many years, been provided with upset end portions at each end on which threads are cut or to which tool joints, i.e. the threaded coupling portions, are typically welded. Upsetting the tubular ends is usually done by forging in preparation for receiving the welded tool joint or threads and such upsetting operations have usually required a number of successive forging steps. For example, U.S. Pat. No. 4,845,972 and U.S. Pat. No. 5,184,495 each require a number of successive forging steps, and in some instances reheating the pipe end in order to work the end of the pipe to achieve the desired degree and shape of upset.
Since forging entails heating of the pipe end to facilitate working the metal and striking the end of the pipe a number of times in the forging die, it is advantageous to minimize the number of steps or passes in upsetting the pipe end, particularly if the entire operation can be achieved without the necessity of having to reheat the pipe at some stage during the process.
Each step in the upsetting operation requires working the pipe and reducing the number of working steps increases the overall efficiency of the upsetting operation so as to conserve both time and money. Since the pipe end must be red-hot during the upsetting operation, accomplishing the forging in as few a number of steps as possible is very advantageous.
It is an object of the present invention to provide a new and improved method and apparatus for upsetting pipe ends and particularly oilfield pipe for receiving welded on tool joints or threads for connecting joints of pipe end-to-end. The present invention employs only two forging steps by the die/mandrel combinations to form an upset end and also to provide a desired finish taper inside the pipe. This is accomplished with first and second dies and corresponding first and second mandrel combinations.
It is also an object of the present invention to combine pressing the forging during the second step to shift an externally displaced portion of the metal inwardly to also provide some internal upset in the pipe end.